In a saucepan or wok, stir-fry the prawns in 2 tablespoons of vegetable oil, for about 2 minutes. Remove the prawns from the pan and set aside.
Stir-fry red curry paste and kaffir lime leaf until fragrant (about 1 minute). Add beans, stir-fry briefly then add coconut cream little by little. Mix well. Add stock, fish sauce, sugar and prawns. Mix well. Taste to adjust the seasoning.
Remove from the heat and sprinkle with sliced kaffir lime leaf.